1. FIELD OF THE INVENTION
The present invention relates to an enclosed extended nip press apparatus for pressing water from a formed web.
More particularly, the invention relates to a seal for sealing the lateral edges of a press blanket during lateral movement thereof.
2. INFORMATION DISCLOSURE STATEMENT
A typical extended nip press includes a backing roll and a cooperating press shoe defining therebetween an extended nip. A press blanket extends in an endless loop through the nip and a lubricant is supplied between the press shoe and an inner surface of the press blanket in order to permit the blanket to move relative to the shoe through the extended nip so that the blanket moves contiguously with a formed web through the nip.
At relatively low operational speeds, lubrication of the press blanket presents few problems. However, at high operational speeds, particularly above 3,000 feet per minute, there exists a tendency for oil mist to be generated within the loop of the press blanket. Such oil mist tends to settle on ancillary equipment including hand rails and access walkways.
Additionally, there exists the possibility of oil contaminating the formed web on the opposite side of the blanket.
In view of the aforementioned problems, many proposals have been made in an attempt to completely enclose the press blanket of an extended nip press. Although the end sealing of such impervious press blanket would present no problem if the blanket remained cylindrical in use, such is not the case. Because of the inherent apple-shaped side-elevational configuration attained by the press blanket in use of the extended nip press, sealing of the lateral edges of the blanket poses relatively complex sealing problems.
In West German Published Application No. DE3338487, inflatable seals are mounted on rotatable heads such that the seals support the inner surface of the blanket adjacent to the lateral edges thereof.
Although the aforementioned arrangement permits movement of the lateral edges of the blanket through the extended nip due to the compressibility of the inflatable seals, there exists the tendency for the lateral edges of the blanket to wander relative to the area of contact with the respective inflatable seal.
U.S. Pat. No. 4,625,376 to Schiel et al sought to overcome the aforementioned problem by the provision of a relatively complex sealing arrangement which included providing a plurality of tongues cut in the lateral edges of the blanket, such tongues being folded radially inward and clamped to the rotating heads.
The present invention provides a simple means for securing the lateral edges of a press blanket against lateral wandering thereof while providing positive sealing against leakage of lubricating oil or mist between the lateral edges of the press blanket and the rotating heads.
Accordingly, the present invention provides a significant improvement over the prior art arrangements and makes a considerable contribution to the enclosed extended nip press apparatus art.
Another object of the present invention is the provision of an enclosed extended nip press apparatus which includes a first and a second plurality of barbs which extend from first and second channels respectively defined by the heads for engaging the lateral edges of the blanket so that during use of the apparatus, lateral movement of the edges of the blanket relative to the heads is inhibited.
Another object of the present invention is the provision of an extended rip press apparatus in which each of the heads defines a circumferential rim, an extension rim extending radially outward from the circumferential rim and a cylindrical rim secured to the first extension rim and disposed coaxially and spaced relative to the circumferential rim such that the circumferential rim, the extension rim, and the cylindrical rim define therebetween the respective channels for the reception therein of the lateral edges of the blanket.
Another object of the present invention is the provision of annular seals disposed within the channels, the seals being disposed on the opposite side of the lateral edges of the blanket relative to the plurality of barbs so that lateral movement of the lateral edges of the press blanket is inhibited.
Another object of the present invention is the provision of an extended nip press apparatus in which each of the heads includes a pair of sectors, the sectors being pivotally secured relative to each other about a pivotal axis extending diametrically across the respective head such that outward pivoting of the sectors about the pivotal axis permits release of the respective lateral edge of the blanket from the associated plurality of barbs.
Another object of the present invention is the provision of an extended nip press apparatus in which the annular seals are inflatable so that inflation of the seals urges the lateral edge of the blanket into locking engagement with the associated plurality of barbs.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.